Signal reproducing system



Sept. 17, 1935. H. s. TASKER 2,014,418

SIGNAL REPRODUCING SYSTEM Filed April 20, 1932 AMPLlFIER INVE NTOR Homer 6. Tas/(er ATTORN EY Patented Sept. 17, 1935 UNITED STATES PATENT OFFICE SIGNAL REPRODUCING SYSTEM Application April 20, 1932, Serial No. 606,338

10 Claims.

This invention relates to signal reproducing systems, and, particularly, to means for combining a plurality of systems for alternative operation and switching from record to record, and

5" to means for balancing the output of selenium cells of the type shown in Hart Patent No. 1,552,926.

When a plurality of records are to be reproduced in sequence, itisdesirable that no pause l 7 shall appear in the sequence of reproduction at the ending of one record and the beginning of the next.

An object of this invention is to combine a plurality of record reproducing systems with a 15 single amplifier and output member, and means for equalizing the signal from the respective reproducers, with means for switching from one to the other without interruption of the signal sequence.

20' Another object is to supply and balance a plurality of record reproducers by means of a single current and control system.

Another object is to switch the input circuit of a single amplifier and amplifier-translating 25 member from one to the other of a plurality of signal reproducers, without interrupting the continuity of signal input thereto.

A further object is to balance a plurality of record reproducers against each other for equal 30 amplitude level of output.-

In the reproduction of sound records in sequence, particularly in synchronism with a motion picture, it is desirable that the transfer from reproducer to reproducer be made without 35 perceptible pause and without change in volume level, such as may occur because of differences in the translating characteristics of the reproducer cell and other adjuncts, such as exciter lights, etc. For this purpose, complicated transfer sys- -0 terms have previously been used, which control and equalize the signal output.

This invention provides a simple potentiometer balancing system, adapted to energize light sensitive cells in an optical record translating system, which, by adjustment of the input current, will give accurate balance between the outputs of a plurality of cells and a simple switching means, which is adapted to transfer the input 50 circuit from one reproducer cell to another without interruption of the signal input.

The objects of this invention are obtained by a combination of a plurality of record reproducing means, including reproducer cells with 55 a single amplifier and translating system, a potentiometer balancing device, and a change-over switch in the amplifier input circuit.

Other objects and structural details of this invention will be apparent from the following description, when read in connection with the 5 accompanying drawing, wherein The single figure is a diagrammatic representation of circuits and apparatus of this inven tion.

In the figure a plurality of eXciter lights I are provided, respectively cooperating with optical sound records 2 and light sensitive cells 3 of the selenium type mentioned in Hart Patent No. 1,552,928, having an internal resistance of approximately 250,000 ohms. An arrangement such as this for translating a sound record into corresponding electric current variations is generally known as a sound head. A battery 1, for the current supply to the cell 3, is provided, shun-ted with a potentiometer resistance 5 having a slider 6. One terminal of each of the respective light sensitive cells 3 is connected to each end of the potentiometer resistance 5.

Suitable energy transferring device such as output transformers l for the respective cells 3 are likewise provided and a terminal of each primary coil therein is connected to a terminal of each cell 3. The other terminals of the respective primary coils are connected together and to a lead to the potentiometer slider 6. The resistance of the potentiometer preferably should be high enough not to discharge the battery too rapidly, and may conveniently be about one hundred thousand ohms. Each assemblage of cell and transformer is shunted by a ballast resister 8 of a value nearly equal to the resistance of the potentiometer 5, dependent upon the range of control desired, such as 50,000 to 100,000 ohms, and a bypass condenser 9 in combination. The secondary coils of the transformer 1 are connected in series to the input circuit of an amplifier system H, the output of which is connected to a translating member such as a loud speaker I2.

The secondaries of the respective transformers I are provided with short circuiting switches M.

In the ope-ration of this system, current is supplied to the exciter lights I; light therefrom is collected by appropriate means upon the record 2 by which it is modulated and from which it is thrown upon the light sensitive cell 3, which may desirably of the selenium cell type. Simultaneously, current from the battery 4 flows through the potentiometer resistance 5. The

voltage drop, across the left-hand portion between the slider contact and the battery connection, forms the energy supply for the lefthand cell, and the voltage drop across the righthand portion of the resistor 5, between the slider 5 and the battery connection, is the energizing potential for the right-hand cell.

There is usually a difference in the translating efiiciency of the respective cells 3, and usually a difference in the intensity of the light provided by the exciter lights I, resulting in a diiference in signal level output from the cells from similar sound records when the cells are energized by equal voltages. The output level of a light sensitive cell is also dependent upon the voltage applied thereto, and, accordingly, movement of the slider 6 will increase the current in one cell and decrease the current in the other, thereby permitting the outputs of the respective cells to be brought to balance and equality of signal level.

One of the records 2 may then be reproduced by means of the exciter light and the photo cell, and the output transferred through the transformer I to the input circuit of the amplifier ll, amplified therein, and translated by a loud speaker 12. When the end of one record is nearly reached, the other record may be put into motion, and, at the proper time, the switch l4, across the secondary of the transformer associated with the second sound record, may be opened, thereby applying the signal vibrations from the secand record to the amplifier, and thereafter, or simultaneously therewith, the other of the switches l4 may be closed, thereby short-circuiting and removing from the amplifier circuit any signal vibrations remaining to be translated from the first record. Alternatively, the two switches 23 may be combined into one double-throw switch, which may be moved from side to side to shortcircuit one or the other of the secondaries of the transformer 'I.

By this means there is thus obtained a simple, inexpensive and accurate means for balancing and equalizing the signal output levels from a plurality of unequal record reproducers, with simple means for translating from one to the other of the respective reproducer circuits.

While there is herein disclosed but a single embodiment of the device of this invention, it is possible to produce still other embodiments thereof without departure from the inventive concept herein disclosed, and it is, therefore, desired that only such limits shall be imposed upon the appended claims as are stated therein or required by the prior art.

The invention claimed is:

1. In combination, a plurality of light sensitive cells, consecutive sound records, traversing means therefor respectively, a source of current for energizing said cells, a single potentiometer device connected between said source and said cells, adapted to adjust the current to said cells, alternating current circuits leading from said cells to a common output, said potentiometer device being connected to said circuits outside the path of the alternating cur 'ents therein.

2. In combination, a plurality of selenium cells, means for traversing consecutive sound records in front or said cells respectively, a plurality of output transformers respectively in series therewith, a single energizing means for said cells, comprising a battery and a potentiometer resistance, and means preventing the alternating current through said transformers from flowing through said resistance.

3. In combination, a plurality of selenium cells, means for traversing consecutive sound records in front of said cells respectively, a plurality of 5 output transformers respectively in series therewith, a single energizing means for said cells, comprising a battery and a potentiometer adapted to adjust the input steady current, a single amplifier member associated with said 10 transformers, and transfer switches therebetween, whereby said potentiometer is adapted to alternately deenergize said cells to shift the reproduction from one cell to the other.

4. The method of fading consecutive records for continuous reproduction which comprises applying energizing potentials to a pair of sound current reproducers, and in gradually varying said potentials simultaneously in opposite senses respectively to fade consecutive sound reproduction from one reproducer to the other.

5. The method of fading from one sound rec- 0rd portion to a consecutive sound record portion and wherein a pair of devices for translating consecutive sound record portions into audio currents is connected to a common output, which method comprises energizing said devices from a common source and in shifting said source from one of said devices to the other and thereby effecting continuity of sound reproduction without thereby varying the impedance to the currents reproduced by said devices.

6. In combination, means comprising a plurality of light sensitive cells for translating consecutive records into a continuity of corresponding current variations, an alternating current circuit for each cell, a common output device connected to said circuits, a source of energizing potential for said cells, and means outside the path of said alternating currents for gradually varying the energizing potentials on said cells from said source in opposite senses respectively to effect continuity of reproduction while shifting reproduction from one cell to another.

7. A fader for two sound film reproducing circuits connected to a common output circuit, said fader comprising a common power supply circuit for the reproducing circuits, means for alternately effectively connecting said power supply circuit to said reproducing circuits, and a by-pass condenser across said power supply circuit and connected in each of said sound reproducing circuits respectively.

8. A fader circuit comprising the combination of a source of current, a resistance in shunt thereto, two light sensitive cells, a connection between one terminal of one of said cells and one terminal of said resistance, a second connection between one terminal of the other cell and another terminal of said resistance, the other terminals of said cells being connected together with a mid-connection therefrom to selected points in said resistance, a source of current for both of said cells, each of said cells having in circuit therewith a transformer for transferring alternating current energy to an output circuit,

a resistance in circuit with said source and each of said cells, and a condenser in shunt to each of said last mentioned resistances.

9. In combination, an output circuit, a plurality of sound heads therefor, means for traversing consecutive sound record sequences in said sound heads respectively, an energizing circuit for said sound heads, and means comprising a single potentiometer device connected between said energizing circuit and said sound heads for shifting and fading reproduction in said output circuit from one of said sound heads to another thereof.

10. In combination, an output circuit, a plurality of sound heads therefor, means for traversing consecutive sound record sequences in said sound heads respectively, an energizing circuit for said sound heads, and means comprising a single potentiometer device connected between said energizing circuit and said sound heads for shifting and fading reproduction in said output circuit from one of said sound heads to another thereof, said output circuit comprising means for bypassing the sound current from said sound heads around said potentiometer device.

HOMER G. TASKER. 

